Each GPU is different simply control temps when OC, do not go over 90C and this GPU will serve you long.
Maximum temps by Nvidia site is 105C
http://nvidia.custhelp.com/app/answers/detail/a_id/2752/~/nvidia-gpu-maximum-operating-temperature-and-overheating
To monitor temps use GPU-Z http://www.techpowerup.com/gpuz/
To check how much heat genre GPU use furmark http://www.ozone3d.net/benchmarks/fur/
To check stability runs some games if you encounter, screen flicker some random dots ect./ drivers failure, game/ PC crash -lower OC.
Anyway main limiting factor for you GPU is weak ram, you can OC without additional cooling you probably cannot push to much this rams.
Each GPU is different simply control temps when OC, do not go over 90C and this GPU will serve you long.
Maximum temps by Nvidia site is 105C
http://nvidia.custhelp.com/app/answers/detail/a_id/2752/~/nvidia-gpu-maximum-operating-temperature-and-overheating
To monitor temps use GPU-Z http://www.techpowerup.com/gpuz/
To check how much heat genre GPU use furmark http://www.ozone3d.net/benchmarks/fur/
To check stability runs some games if you encounter, screen flicker some random dots ect./ drivers failure, game/ PC crash -lower OC.
Anyway main limiting factor for you GPU is weak ram, you can OC but no to much